Most research has found that diet trumps exercise as a means of losing weight.

They both play a part, but eating less is the key to shrinking your waistline rather than working out or going for long jogs.

But what happens when you’ve lost the weight and want to keep it off?

A new study from the University of Colorado Anschutz Health and Wellness Centre (AHWC) found that “successful weight-loss maintainers rely on physical activity to remain in energy balance (rather than chronic restriction of dietary intake) to avoid weight regain”.

In other words, physical activity does more to maintain substantial weight loss than diet.

In the study, “successful weight-loss maintainers are individuals who maintain a reduced body weight of 30 pounds (about 13.6 kilograms) or more for over a year”.

Key to their success was walking at least 12,000 steps a day.

Dr Danielle Ostendorf, a postdoctoral fellow at AHWC and co-author of the new study, said in a statement from the university: “This study addresses the difficult question of why so many people struggle to keep weight off over a long period.

“By providing evidence that a group of successful weight-loss maintainers engages in high levels of physical activity to prevent weight regain – rather than chronically restricting their energy intake – [it] is a step forward to clarifying the relationship between exercise and weight-loss maintenance.”

So how was this evidence collected?

The study compared three group of participants:

• The first group (25 individuals) were previously overweight or obese but now weighed about 68 kilograms. On average, they’d previously weighed more than 80 kilograms. They were at the top end of the health range with a Body Mass Index (BMI) of 24.1. A BMI of 25 is the threshold for being overweight. These participants had successfully kept the weight off for a year
• The second group (27 individuals) were also of a healthy weight similar to the weight-loss maintainer group, with an average BMI of 23
• The third group (28 individuals) weighed about 96 kilograms, with a BMI of 34.3, which put them well in the obese category.

The strategy of the study was to compare the number of calories the participants burnt from body movement, the total daily energy expenditure (an estimation of how many calories they burnt when exercise was taken into account), and an estimation of how many calories were being consumed by the participants.

For these measurements, the researchers used what is often described as the ‘gold standard’ tool: The doubly labelled water method.

This method allows researchers to “precisely determine an individual’s energy expenditure through collecting urine samples over one to two weeks after people are given a dose of doubly labelled water.

Short version: It’s a fancy and costly way of estimating how much carbon dioxide is produced in the body as a result of nutrients being converted into energy.

The researchers also measured the participants’ metabolic rate “in order to understand how much of the total daily energy expenditure is from energy expended at rest versus energy expended during physical activity”.

The findings

The total calories burned and consumed each day by the weight-loss maintainers was significantly higher (300 kcal/day) compared with that of participants with normal body weight.

But it wasn’t significantly different from that of the participants with obesity.

In other words, the participants who had maintained their weight loss were eating about the same amount (in calories) as the participants from the obesity group.

But the amount burned in physical activity by weight-loss maintainers was significantly higher (180 kcal/day) compared with that of the normal body weight group and the obesity group.

Also, the weight-loss maintainer group did significantly higher numbers of steps per day (12,000), compared to participants at a normal body weight (9000) and participants with obesity (6500).

The researchers thus concluded: “This group of successful weight-loss maintainers are consuming a similar number of calories per day as individuals with overweight and obesity but appear to avoid weight regain by compensating for this with high levels of physical activity.”

Not convinced?

The researchers say their findings “are consistent with results from the longitudinal study of The Biggest Loser contestants, where physical activity energy expenditure was strongly correlated with weight loss and weight gain after six years”.